Khalifa AA, Abdelaal AM, Moustafa MM. Does surgeon handedness affect the outcomes after primary total knee arthroplasty? A retrospective cohort study. World J Orthop 2026; 17(2): 113696 [DOI: 10.5312/wjo.v17.i2.113696]
Corresponding Author of This Article
Ahmed A Khalifa, MD, Assistant Professor, FRCS, Department of Orthopaedic, Qena Faculty of Medicine and University Hospital, South Valley University, Kilo 6 Qena-Safaga Highway, Qena 83523, Qina, Egypt. ahmed_adel0391@med.svu.edu.eg
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Orthopedics
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Retrospective Cohort Study
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This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Feb 18, 2026 (publication date) through Feb 4, 2026
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World Journal of Orthopedics
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Khalifa AA, Abdelaal AM, Moustafa MM. Does surgeon handedness affect the outcomes after primary total knee arthroplasty? A retrospective cohort study. World J Orthop 2026; 17(2): 113696 [DOI: 10.5312/wjo.v17.i2.113696]
Author contributions: Khalifa AA carried out the study conception and design; Khalifa AA and Moustafa MMA performed the measurements, data acquisition, assessment, literature search, and preparation of the images and tables; Khalifa AA carried out the statistical analysis; Khalifa AA, Abdelaal AM, and Moustafa MMA drafted the manuscript; Abdelaal AM and Khalifa AA performed critical revisions. All authors read, discussed, and approved the final manuscript.
Institutional review board statement: This study was reviewed and approved by the Ethics Committee of Faculty of Medicine, Assiut University, No. 04-2025-300657.
Informed consent statement: This study was conducted retrospectively using anonymized radiographic and clinical data. No patient-identifiable information was collected or reported, and no direct patient contact occurred. Therefore, the requirement for informed consent was waived in accordance with the ethical standards of our institutional review board (No. 04-2025-300657) and the Declaration of Helsinki and its later amendments, as well as the International Committee of Medical Journal Editors recommendations.
Conflict-of-interest statement: The authors declare no conflict of interest concerning this manuscript.
STROBE statement: The authors have read the STROBE Statement-checklist of items, and the manuscript was prepared and revised according to the STROBE Statement-checklist of items.
Data sharing statement: All data are included within the manuscript; however, the raw data could be provided upon reasonable written request to the corresponding author.
Open Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Ahmed A Khalifa, MD, Assistant Professor, FRCS, Department of Orthopaedic, Qena Faculty of Medicine and University Hospital, South Valley University, Kilo 6 Qena-Safaga Highway, Qena 83523, Qina, Egypt. ahmed_adel0391@med.svu.edu.eg
Received: September 1, 2025 Revised: October 2, 2025 Accepted: December 10, 2025 Published online: February 18, 2026 Processing time: 156 Days and 12.6 Hours
Abstract
BACKGROUND
Various factors affecting the outcomes after primary total knee arthroplasty (TKA) have been investigated in the literature; however, the effect of surgeon handedness on outcomes has rarely been addressed.
AIM
To assess whether the radiological and functional outcomes differ between right and left primary TKA when operated by right-handed surgeons.
METHODS
A retrospective evaluation of 370 TKAs performed by right-handed surgeons [47.8% right TKAs, dominant side (Group D), and 52.2% left TKAs, non-dominant side (Group N)]. The radiological outcomes were the overall alignment measured as the hip-knee-ankle (HKA) angle, and the tibial and femoral component alignment in the coronal plane measured as the medial tibial proximal angle (MPTA) and mechanical lateral distal femoral angle (mLDFA). The percentage of each alignment outside the accepted safe zone values (outliers) were calculated. The functional outcome at the last follow up was evaluated per the Knee Society Score (KSS) System for 206 knees only.
RESULTS
There were no difference in patients' basic characteristics or in postoperative radiological or functional outcomes between Group D and Group N as follows: HKA, 177.96° ± 3.13° vs 178.55° ± 3.38° (P = 0.082), MPTA, 88.90° ± 2.61° vs 89.43° ± 2.71° (P = 0.056), mLDFA, 90.16° ± 2.54° vs 89.76° ± 2.53° (P = 0.140), and KSS, 80.59 ± 14.73 vs 79.56 ± 15.64 (P = 0.628). There was no significant difference in the percentage of outliers in the HKA and mLDFA between groups. For the MPTA, Group D had significantly more implants within the safe zone than Group N, 53.7% vs 41.4% (P = 0.022). There was no difference regarding using intramedullary (IM) vs extramedullary (EM) alignment for the tibial cut between both groups (P = 0.687). In Group D, there was no significant difference in mean MPTA between IM (88.86° ± 3.26°) and EM (88.93° ± 1.76°) methods (P = 0.862); however, EM resulted in significantly fewer outliers compared to IM (29.2% vs 63.6% respectively; P < 0.001). In Group N, the EM method produced a significantly more valgus alignment than IM (90.38° ± 1.99° vs 88.56° ± 3.00°, P < 0.001), but this did not translate into a significant reduction in outliers (P = 0.650).
CONCLUSION
The overall radiological and functional outcomes after primary TKA were unaffected by the surgeon's handedness; however, the placement of the tibial component was significantly more precise on the dominant side with fewer outliers.
Core Tip: Factors affecting primary total knee arthroplasty (TKA) outcomes could be related to the patient, surgical technique, and the surgeon. One rarely investigated surgeon-related factor is surgeon handedness. We evaluated 370 knees operated by right-handed surgeons, where 177 TKAs were right (dominant side) and 193 were left (non-dominant side). We found no difference between sides regarding the overall limb and individual component coronal plane alignment; furthermore, there was no difference in the functional outcomes between sides, but there were fewer tibial component outliers in the dominant side. Surgeons operating on the non-dominant side should pay attention during the tibial cut and implant insertion.
Citation: Khalifa AA, Abdelaal AM, Moustafa MM. Does surgeon handedness affect the outcomes after primary total knee arthroplasty? A retrospective cohort study. World J Orthop 2026; 17(2): 113696
Although total knee arthroplasty (TKA) is considered one of the most successful procedures with excellent functional and radiological long-term outcomes, a considerable subset of patients (up to 21%) are unsatisfied with the outcomes[1-3]. Moreover, up to 4%-8% of TKAs require revision within 10 years for several causes, most commonly for periprosthetic joint infection and aseptic loosening, which is partially attributed to overall limb or individual component malalignment, partially leading to accelerated polyethylene wear[4-10].
Outcomes and survival rates after TKA are influenced by many variables, some of which could be related to the patient, the surgeon, the prosthesis, and the surgical technique[10-12]. Of the technical intraoperative factors, proper ligament balancing and optimum component placement in all planes eventually lead to appropriate overall limb alignment per the desired planned alignment target[13-17].
Many alternative TKA alignment targets have been proposed in recent years, and various technologies have been introduced to improve component placement and alignment and reach the alternative alignment targets, such as computer navigation and robotic-assisted TKA[16,18,19]. However, many surgeons still aim for the classic mechanical alignment (MA); furthermore, manual instrument-derived MA is considered the gold standard practice, especially for surgeons unable to use advanced technologies[16,18-21].
Proper guide placement, bony cut execution, and optimum component insertion are crucial for obtaining the desired limb and individual component alignment during MA-TKA using manual instruments. Investigating the possible factors affecting the surgeon's accuracy while performing these steps will inform the surgeons to how to avoid them.
One factor to pay attention to during total hip arthroplasty (THA) is the surgeon's handedness and whether the surgeon is operating on the dominant or non-dominant side, which has been reported to have an effect on radiological and functional outcomes[22-26]. Such an investigation is scarce, with only four studies exploring such an issue, three on TKA and one on unicompartmental knee arthroplasty (UKA)[27-30].
The current study's primary objective was to investigate whether operating on the dominant vs non-dominant side affects the radiological and functional outcomes in surgeons aiming for MA-TKA while using manual instruments. The secondary objective was to estimate the incidence of outliers in the whole lower limb and individual component coronal alignment between both sides.
MATERIALS AND METHODS
Study design
This was a single-center retrospective cohort study approved by the institute’s ethical committee (IRB No. 04-2025-300657). The ethical considerations were followed according to the Helsinki Declarations, and the study was reported per STROBE guidelines[31].
Research participants, inclusion, and exclusion criteria
The records of patients who underwent primary TKA over 5 years were reviewed. Patients who were diagnosed with primary knee osteoarthritis (OA) or rheumatoid arthritis, those who had a full radiological record preoperative and postoperative (within the first three months), properly obtained long film standing anteroposterior (AP) plain radiographs showing hip-knee-ankle (HKA), and functional outcome scores obtained at least 6 months postoperatively were included in the study. Exclusion criteria were: Patients who had complex primary TKA (posttraumatic arthritis, extraarticular deformities, after corrective osteotomies, and if a stem on the tibial or femoral sides was used), simultaneous bilateral TKA, revision TKA, patients who had ipsilateral THA, and those with incomplete records. Out of 681 records evaluated, only 370 were eligible for inclusion: 177 right TKAs (dominant side, Group D) and 193 left TKAs (non-dominant side, Group N). Only 206 patients (100 from Group D and 106 from Group N) had functional outcomes.
Surgical details
All surgeries were performed by fellowship-trained right-handed surgeons (five surgeons with at least 3 years of independent arthroplasty practice) working at the same institution. Anesthesia was based on the patient's condition and the anesthesiologist's preference; all surgeries were performed under tourniquet control, and the surgeon always stood on the same side of the surgery. Posterior stabilized implants were used in all surgeries, adopting the measured resection philosophy and aiming at neutral (180°) MA[32,33]. A medial parapatellar approach was utilized in all cases, starting with the distal femoral cut guided by an intramedullary (IM) rod. The angle of the distal femoral cut was based on the preoperative estimation of the valgus correction angle, which is the angle between the femoral mechanical and anatomical axes[32], and the remaining femoral cuts were performed using a 4-in-1 cutting block after adjusting the femoral rotation according to various local anatomical landmarks (transepicondylar axis, Whiteside line, or the posterior condylar line)[34]. On the tibial side, a 90° tibial cut in the coronal plane was made with 5˚ of posterior slope, which was achieved using IM or extramedullary (EM) guides per surgeon preference, which were used in 188 and 182 patients, respectively[35]. The patella was not resurfaced in any of the patients. Per our institution's protocol, postoperative care and rehabilitation were the same for all patients[36].
Radiographic and functional assessment and outcomes
Radiographic: AP HKA plain radiographs were used to evaluate coronal plane alignment[37]. The whole lower limb alignment (HKA angle) was measured as the medial angle between the femoral and tibial mechanical axes. Tibial implant alignment was assessed by the medial tibial proximal angle (MPTA) as the medial angle between a line tangential to the tibial baseplate and the mechanical axis of the tibia. Femoral implant alignment was assessed by the mechanical lateral distal femoral angle (mLDFA) as the lateral angle between the femoral mechanical axis and a line tangential to the distal points of the medial and lateral femoral condyles (Figure 1).
Figure 1 The radiological parameters measured in the coronal plane, hip to knee to ankle angle indicated by the white arrow.
The medial proximal tibial angle is indicated by the green arrow. The mechanical lateral distal femoral angle is indicated by the organe arrow. HKA: Hip to knee to ankle; MPTA: Medial proximal tibial angle; mLDFA: Mechanical lateral distal femoral angle.
The following ranges for the coronal plane alignment were accepted as safe zones: 180° ± 3° for the HKA[12,38,39], 90° to 87° for the MPTA[40], and 90° ± 3° for the mLDFA[41,42]. Measurements outside these ranges were considered outliers.
Functional: Assessment was performed according to the Knee Society Score (KSS)[43].
Statistical analysis
Data were analyzed using the SPSS, version 26.0 for Windows. Data were tested for normality using the Shapiro-Wilk test. Qualitative data were expessed as frequency and percentage, while quantitative data were expressed as mean ± SD (range). The student t-test and the χ2 test were used to compare variables between groups as appropriate. To estimate the relative likelihood of achieving alignment within the defined safe zone between comparative groups, odds ratios (OR) with 95% confidence intervals (CI) were calculated. A P value < 0.05 was considered statistically significant.
RESULTS
Participants' characteristics
A total of 370 knees were evaluated, 177 (47.8%) right and 193 (52.2%) left, in patients having a mean age of 58 ± 9 years. Most of the patients were diagnosed with knee OA (79.7%), and the majority had preoperative varus deformity (93.8%). There were no differences in the basic demographic characteristics or the preoperative diagnosis between the two groups (Table 1).
Table 1 Basic characteristics of included patients, n (%).
Coronal plane alignment: HKA: There was no difference regarding the overall limb alignment in the coronal plane between group D and group N, preoperatively (167.88° ± 9.34° vs 167.94° ± 8.82°, respectively), P = 0.956, and postoperatively (177.96° ± 3.13° vs 178.55° ± 3.38°, respectively), P = 0.082. There was a significant postoperative improvement of HKA compared to the preoperative measurements for both groups: Group D (167.88° ± 9.34° vs 177.96° ± 3.13°, P < 0.001) and Group N (167.94° ± 8.82° vs 178.55° ± 3.38°, P < 0.001).
MPTA and mLDFA: There were no significant differences between groups for tibial and femoral component alignment. For the MPTA, Group D vs Group N: 88°.90 ± 2.61° vs 89.43° ± 2.71°, P = 0.056. For the mLDFA, Group D vs Group N: 90.16° ± 2.54° vs 89.76° ± 2.53°, P = 0.140 (Table 2).
Table 2 Comparison of coronal alignment between both sides, n (%).
Outliers: There was no significant difference in the percentages of outliers (outside the determined safe zones) regarding the HKA and mLDFA between groups. For the MPTA, Group D had significantly more implants within the safe zone for tibial implant alignment than Group N, 53.7% vs 41.4%, P = 0.022 [OR 1.63 (95%CI: 1.08-2.48)] (Table 2 and Figure 2).
Figure 2 Comparing the percentages of limb and individual component alignment within the accepted safe zones between both sides.
HKA: Hip to knee to ankle; MPTA: Medial proximal tibial angle; mLDFA: Mechanical lateral distal femoral angle.
Comparing techniques for tibial implant insertion
There was no difference between IM vs EM alignment for the tibial cut between groups (P = 0.687). There was no significant difference in mean MPTA between IM (88.86° ± 3.26°) and EM (88.93° ± 1.76°) methodsiIn Group D (P = 0.862); however, EM resulted in significantly fewer outliers compared to IM, P = 0.001, and OR: 4.24 (95%CI: 2.26-7.96). In Group N, the EM method produced a significantly more valgus alignment than IM (90.38° ± 1.99° vs 88.56° ± 3.00°, P < 0.001), but this did not translate into a significant reduction in outliers (P = 0.650). Comparing the EM technique in both groups, there were fewer outliers in Group D compared to Group N, P = 0.001 [OR 3.67 (95%CI: 1.98-6.80)] (Table 3).
Table 3 Comparing the methods used for tibial component insertion, n (%).
The overall mean follow up time was 29.10 ± 27.14 months (8 to 132), (29.53 ± 26.92 months for Group D, vs 28.67 ± 27.35 months for Group N, P = 0.703). There was a significant improvement (P < 0.001) in the KSS for both groups as reported in the last follow up, Group D, preoperative vs postoperative, 40.36 ± 12.41 (14 to 55) vs 80.59 ± 14.73 (65.86 to 95.32), and Group N, preoperative vs postoperative, 41.69 ± 11.10 (14 to 75) vs 79.56 ± 15.64 (63.92 to 95.20). There was no significant difference between the two groups in preoperative or postoperative KSS; P = 0.416 and P = 0.628, respectively.
DISCUSSION
The results of the current study showed that functional and overall limb and individual component coronal plane alignment were not affected by the surgeon's handedness or whether operating on the dominant or non-dominant side. However, more tibial components were significantly inserted within the accepted safe zone on the dominant side. Furthermore, we found some discrepencies between our results and previous studies (Table 4).
Table 4 Summary of the results reported in the previous studies.
For the right-handed surgeons: No difference in the radiological outcomes regardless of the side of surgery and regardless of their standing position during surgery. For the left-handed surgeons: A significant difference in the HKA [-1.5 (-2.6 to -1) vs -3 (-4.5 to -2), P = 0.01] for surgeon B. A significant difference in the MPTA [0 (-1 to 0.5) vs 1 (0-2), P < 0.01] for surgeon D
In the current study, we achieved significant improvement of the HKA postoperatively in all patients compared to the preoperative values (P = 0.001), and there was no difference between the dominant and non-dominant sides (P = 0.082). Furthermore, the tibial and femoral implant alignment did not differ between both sides.
Liu et al[28] evaluated the effect of surgeon handedness on component alignment during TKA. They retrospectively evaluated 100 TKAs (72 unilateral and 14 bilateral) in 86 patients, divided equally between right and left sides. All knees were operated on by a single right-handed surgeon who operated while standing on the operated side. They reported no difference in the operative time between groups, 108.7 ± 22.1 vs 113.1 ± 16.3 for dominant and non-dominant sides, respectively (P = 0.262). Coronal plane alignment parameters significantly improved postoperatively in both groups compared to the preoperative values; however, there were no significant differences between the dominant and non-dominant sides as follows: HKA 1.9 ± 4.4 vs 2.3 ± 3.8 (P = 0.634), MPTA 90.0 ± 2.5 vs 90.1 ± 2.6 (P = 0.855), and mLDFA 88.6 ± 2.8 vs 88.4 ± 2.5 (P = 0.616).
To evaluate the effect of surgeon handedness on UKA, Cao et al[29] retrospectively assessed 94 UKAs (49 left and 45 right) performed by a right-handed surgeon in patients with a mean age of 63.5 ± 9.0 years. There were no significant differences in preoperative parameters between right and left knees. Although there were no differences in operative time or complication rates (intra- and postoperative) between both sides, the authors noticed a trend toward a higher complication rate on the non-dominant (left) side (8.2% vs 6.7%). There was a significant improvement in coronal plane limb alignment per the femoro-tibial angle and HKA angles, and there was no significant difference between sides. Regarding individual component alignment, the tibial varus-valgus alignment was 3.57° ± 1.42° on the left and 3.19° ± 1.56° on the right (P = 0.45). In contrast, the femoral component varus-valgus alignment was significantly better in the dominant (right) compared to the non-dominant (left) side, 7.81° ± 2.43° vs 7.05° ± 2.90°, respectively (P = 0.04).
Rate of alignment outliers
The overall outlier rates varied among studies, ranging from 18% to 53% for the HKA, 13% to 50% for the lateral distal femoral angle (LDFA), and 2% to 25% for the MPTA[17]. In the current study, the incidence of alignment outliers for the whole cohort was 35.4% for the HKA, 20.8% for the mLDFA, and 52.7% for the MPTA. We did not find a difference in the incidence between the two groups in the HKA and mLDFA; however, MPTA outliers were significantly higher in the non-dominant side, with the dominant side 1.6 times more likely to fall within the MPTA safe zone.
Jaglarz et al[30] investigated the effect of surgeons' handedness and where they stand at the operative table on radiological outcomes (overall and individual component alignment) after primary TKA, where the aim was MA. They included 200 patients diagnosed with knee OA with varus deformity, who were operated on by four surgeons (50 TKA each). Surgeons were divided according to their handedness and standing position into surgeon A: Right-handed, always standing on the right side; surgeon B: Left-handed, always standing on the left side; surgeon C: Right-handed, standing on the operated limb side; and surgeon D: Left-handed, standing on the operated limb side. The authors reported significant differences regarding the deviation from a neutral HKA between the right and left sides for surgeon B (HKA: Left -1.5°, range = -2.6 to -1 vs right -3°, range = -4.5 to -2; P = 0.01), and in the tibial component orientation for surgeon D (MPTA: Left 0°, range = -1 to 0.5 vs right 1°, range = 0-2; P < 0.01). They reported that for both of the previous surgeons, a higher deviation from the MA angles and implant positioning occurred on the surgeon's less convenient operation site.
IM vs EM alignment technique for tibial implant insertion
The issue of comparing the accuracy of IM vs EM techniques for guiding the tibial cut has been thoroughly reported in the literature, and some authors have reported that there are no differences between the two techniques[35,44].
Although comparing both techniques was not a primary objective of the current study, we did not identify a difference regarding MPTA in the dominant side between EM vs IM techniques (P = 0.862). Furthermore, EM-guided tibial component insertion was more accurate, leading to significantly fewer outliers (about 4 times less, OR 4.24, 95%CI: 2.26-7.96) compared to the IM technique. In the non-dominant side, the IM technique resulted in significantly better tibial component alignment (P = 0.001), whereas the EM method led to a more valgus alignment. However, this did not reflect a difference in the incidence of outliers when comparing IM vs EM alignment within the non-dominant side (P = 0.650). Comparing both sides, there was no difference in the incidence of outliers when using the IM technique. However, the EM technique showed significantly lower outliers (about 3.7 times less, OR 3.67, 95%CI: 1.98-6.80) in the dominant compared to the non-dominant side (P = 0.001).
Functional outcomes
Mehta and Lotke[27] were the first to evaluate the effect of surgeon handedness on outcomes after primary TKA. In their study, a single right-handed surgeon performed 728 primary TKAs (377 right and 351 left), where he always stood on the operated side (the same as in the current study); they reported significantly better Knee Society (KS) functional and pain outcomes in the dominant side both 6 six weeks and 1 year of follow up. At 6 weeks, the dominant vs non-dominant side KS function score was 56.1 vs 52.4, respectively, P = 0.006, and the difference was maintained through 1 year (73.5 vs 70.5, P = 0.03). Similarly, the KS pain score at 6 weeks was 91 vs 82 (P = 0.006), and 95 vs 83 (P = 0.029) at 1 year.
On the contrary, we did not find any difference between both sides regarding the functional outcomes, consistent with the results reported by Cao et al[29], who found no differences in the functional outcomes (KSS and Oxford Knee Score) between both sides after a mean follow up of 26.7 ± 3.2 months. Furthermore, after a mean follow up of 22 months, Liu et al[28] reported no significant difference in the functional outcomes according to the Hospital for Special Surgery (HSS) score, 87.2 ± 4.3 for the dominant side and 86.8 ± 5.0 for the non-dominant side (P = 0.639).
The importance of proper component coronal plane alignment
Although we did not report differences in the functional outcomes or radiological alignment between groups, it is worth mentioning that individual component malalignment might be a cause of lower functional outcomes, as reported in a study by Luan et al[17] where the authors evaluated the overall limb alignment (HKA) and individual component alignment in the coronal, sagittal, and axial planes. They divided their patients according to the clinical results per the HSS knee scoring system into excellent, good, and not good. They found a significant difference in the LDFA among the three groups, where the poor group reported the highest valgus orientation (P = 0.05), and the same group had the lowest femoral component sagittal alignment as well (P = 0.001). Furthermore, limb malalignment in general and the tibial component in particular have been shown to affect the outcomes and implant survival after TKA[7-9,45].
Regarding the tibial component coronal plane alignment, we reported more tibial components located within the accepted alignment safe zone when the surgeons operated on the dominant side. Notably, tibial component malalignment in the coronal plane was associated with increased stresses on the medial side when it was in varus malalignment and increase in the medial ligaments force when it was in valgus malalignment[46], ultimately leading to early failures. Furthermore, such a malalignment was associated with poor patient outcomes and lower satisfaction rates after TKA, in addition to other factors[47].
Possible reasons behind the surgeon's handedness effect on TKA outcomes
Such a handedness effect, and whether operating on the dominant or non-dominant side, on surgeons' performance and training, has been investigated among various surgical specialties[29,48-51]. In orthopedic and traumatology in general and joint replacement surgery in particular, where anatomical areas are usually presented bilaterally, this issue was of concern and has been discussed by many authors with conflicting results. However, the conclusion is that surgeons handedness affects functional and radiological outcomes, with surgeons reporting better comfort and outcomes when operating on the dominant side[26-28,30,48].
Relatively superior outcomes when operating on the dominant side could be explained by better control over skilled activities when the surgeon is in an advantageous and comfortable position; furthermore, a better spatial orientation ability has also been suggested[52-55]. Hanna et al[56] suggested three reasons affecting surgeons' performance based on their comparison of psychomotor abilities between right and left-handed surgeons during endoscopic surgery: Reduced tactile feedback, kinematic restriction, and the time needed to process operating field indirect images. Surgeon handedness and whether the surgeon is operating on the dominant or non-dominant side were added as a fourth reason by Mehta and Lotke[27].
Although we did not investigate which particular step was performed by the surgeons’ dominant or non-dominant limb, various studies reported that the dominant limb is more powerful than the non-dominant side, with better control of skilled activities, refined and more accurate motor control, faster manipulation, and longer time to fatigue, which may play a role in the accuracy of particular surgical steps[52-55].
Where should the surgeon stand during TKA?
Each surgeon adopts his or her own comfortable position while performing TKA. From our perspective, operating on the dominant side is more comfortable if the surgeon prefers to stand on the side of the operated knee. After evaluating four different standing options, Jaglarz et al[30] concluded that surgeons performing TKAs and operating from the less comfortable (non-dominant) side should pay more attention to ensure that the MPTA and HKA angles are correct.
A study by Sánchez-Robles et al[57] evaluated ergonomic risk to determine the best position where a right-handed surgeon should stand while performing left TKA (non-dominant side). The authors tested four different positions: Position 1, on the opposite side, position 2, on the same side, position 3, between the patient's legs, and position 4, facing the left knee (standing at the foot side). They performed ergonomic analysis through the Rapid Entire Body Assessment (REBA) method, where lower scores mean better ergonomics. The scores were 7 to 6.5 for position 1, 6.17 to 5.5 for position 2, 5.92 to 5.5 for position 3, and 3.75 to 3.42 for position 4. They concluded that standing facing the patient's knee is the best ergonomic position for a surgeon operating on the non-dominant side.
Furthermore, Sánchez-Robles et al[57] videotaped 12 steps of performing TKA. They reported a higher REBA score above 7 (unfavorable ergonomics and correction is necessary) when a surgeon operates on the non-dominant side during placement of the tibial and femoral cutting guides and performing distal and AP femoral cuts. The previously mentioned steps are crucial for proper tibial and femoral component positioning.
The current study has some limitations. First, the study's retrospective nature can introduce bias, particularly because we only reported functional outcomes of 55.7% of the patients. However, to ensure proper representation, we compared the basic characteristics of patients with functional outcomes and those without, revealing no significant difference. Second, we only evaluated the alignment in the coronal plane, while sagittal and axial plane alignment were not investigated. It is worth noting that Liu et al[28] evaluated the individual component positioning in the sagittal plane; they reported that the femoral component sagittal plane orientation, measured as the posterior distal femoral angle (PDFA), showed a significant difference between both sides, where PDFA for the dominant vs non-dominant side was 90.0 ± 3.3 vs 88.4 ± 3.9, respectively, P = 0.032, with more femoral components placed within the neutral position in the dominant group (72% vs 66%), but the difference did not reach statistical significance (P = 0.517). However, the incidence of femoral component malposition was significantly higher in the non-dominant group (20% vs 6%, P = 0.037). Furthermore, they reported no difference regarding the two groups' tibial component alignment in the sagittal plane.
Third, having the majority of preoperative alignments in varus, with few patients having valgus deformity, prevented statistically robust subgroup analysis to evaluate the surgeon's handedness effect in various deformity patterns.
Fourth, all operating surgeons were experienced right-handed, and there were no junior or left-handed surgeons included in the analysis, which may affect the generalizability of the results, as experienced surgeons might have learned with time how to compensate for changing positions while operating on both sides. It is worth noting that the significant differences reported in Jaglarz et al's study[30] were of left-handed surgeons (in HKA for surgeon B and in the MPTA for surgeon D), indicating that further studies including more left-handed surgeons are warranted.
Fifth, we only included patients who had unilateral TKA. Evaluating patients with bilateral TKA could provide a better internal control and more powerful statistical analysis; however, such a comparison was included in the study by Mehta and Lotke[27]. Their study included 40 bilateral TKAs, and the authors reported that the results of knee extension and KS function and pain scores were significantly better in the dominant side. Still, they reported no significant difference in knee flexion range or the overall range of motion between both sides.
Sixth, we did not report the incidence of complications or revisions, which is crucial to correlate with alignment outliers. Lastly, we did not perform correlation analysis to investigate other factors affecting the radiological and functional outcomes besides the surgeon's handedness.
CONCLUSION
The overall limb alignment in the coronal plane and individual component alignment after primary TKA did not differ between the dominant and non-dominant sides for right-handed surgeons. However, the incidence of inserting the tibial implant outside the accepted safe zone is significantly higher when operating on the non-dominant side. Moreover, using an EM guide for tibial cut resulted in fewer outliers on the dominant side, while on the non-dominant side, the IM technique resulted in significantly better tibial component alignment. Although the differences reported might be considered minimal, considering the possible effect of surgeon handedness on proper implant placement, especially for the tibial implant when operating on the non-dominant side, might be beneficial for young and low-volume surgeons. Future studies, including young and left-handed surgeons as well as long-term follow-up, are warranted to further investigate the effect of the surgeon's handedness on TKA outcomes.
Footnotes
Provenance and peer review: Invited article; Externally peer reviewed.
Peer-review model: Single blind
Specialty type: Orthopedics
Country of origin: Egypt
Peer-review report’s classification
Scientific Quality: Grade B, Grade B, Grade C
Novelty: Grade B, Grade B, Grade D
Creativity or Innovation: Grade C, Grade C, Grade D
Scientific Significance: Grade B, Grade C, Grade D
P-Reviewer: Julfiqar M, Assistant Professor, India; Ksheerasagar VP, MD, Consultant, India S-Editor: Qu XL L-Editor: Filipodia P-Editor: Zhao YQ
Inui H, Yamagami R, Kono K, Kawaguchi K. What are the causes of failure after total knee arthroplasty?J Joint Surg Res. 2023;1:32-40.
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Bhanushali A, Holder C, McAuliffe MJ, Martin D, Smitham PJ. Revision Rates After Total Knee Arthroplasty Among Surgeons of Varying Experience: An Australian Orthopaedic Association National Joint Replacement Study.J Arthroplasty. 2025;S0883-5403(25)00755.
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Vermue H, Andriollo L, Servien E, Batailler C, Lustig S. Functional knee positioning in total knee arthroplasty: Rationale and current evidence.J Joint Surg Res. 2025;.
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Mehta S, Lotke PA. Impact of surgeon handedness and laterality on outcomes of total knee arthroplasties: should right-handed surgeons do only right TKAs?Am J Orthop (Belle Mead NJ). 2007;36:530-533.
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Jaglarz D, Kowalczewski J, Dudek P, Pankowski R, Marczak D, Grzelecki D. The influence of the surgeon's handedness and standing position at the operating table on the radiological outcomes in primary total knee arthroplasty.Knee. 2024;50:147-153.
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Silva JD, Nunes B, Duarte F, Raposo F, Valente L, Antunes A, Oliveira P, Sousa A. Effect of tibial alignment in early failure in total knee arthroplasties.Rev Chi Orthop Traumatol. 2016;102:S80.
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Jee H, Park J. Comparative Analyses of the Dominant and Non-Dominant Upper Limbs during the Abduction and Adduction Motions.Iran J Public Health. 2019;48:1768-1776.
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Sánchez-Robles M, Díaz-Martínez FJ, León-Muñoz VJ, Marín-Martínez C, Murcia-Asensio A, Moreno-Cascales M, Lajara-Marco F. Ergonomic Evaluation of Different Surgeon Positions for Total Knee Arthroplasty Surgery.Appl Sci. 2023;13:11842.
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